Nine systems were prepared containing
Gelucire 50/13 and various amounts (9-18-36-45% w/w) of
Lutrol F68 and
F127 in the presence and in the absence of 10% w/w of
olanzapine and formulated as a solid dispersion in the form of
microspheres by ultrasound (US)-assisted spray congealing. Thermal analysis, using differential scanning calorimetry (DSC) and thermomicroscopy (HSM), suggested the presence of particles of reduced size of
olanzapine precipitated inside the
microspheres. The
microspheres were also studied by means of electron microscopy (SEM) for their shape and aspect, by some image analysis parameters (fractal dimension) and using Energy-dispersive X-ray (X-EDS) and micro-Raman spectroscopy to qualitatively evaluate the composition of different points of the surface. The surface of the
microspheres displayed a non-homogeneous distribution of the
drug by the presence of
wart-like protuberances, whose number increases as the
Lutrol content of the systems increases. The same systems in the absence of US, obtained after cooling the molten mixtures, lack these structures and only a very few of them can be found. The blooming of the surface was hypothesized as related to crystallization or phase de-mixing or
lipid component diffusion of the carrier mixture inside the cooling mass subjected to ultrasound vibration. Ultrasounds accelerate the physical changes concerning carriers and
drug, outlining the importance of ultrasound to achieve stability for formulations of this type. The
microspheres de-aggregate on contact with the dissolution medium and release the
drug with a bimodal mode according to the
Lutrol content.